1. Field of Invention
The inventions described in this disclosure relate generally to apparatus and methods for performing medical procedures and, more particularly, to apparatus techniques for immobilizing tissue or providing frame of reference for performance of medical procedures.
2. Discussion of Related Art
The inventions described in this application relate generally to medical imaging and sensing of anatomical features, procedures performed in connection with that imaging and sensing, and the tools used for the procedures and sensing. The inventions will be described in the context of medical imaging for surgical procedures to be performed on soft tissue which is susceptible to movement during a procedure, such as a woman's breast, and more particularly related to marker placement (such as needle localization of implanting or injecting a marker), biopsies and open surgical removal of a suspected cancerous lesion within a breast. While certain aspects of the present inventions are uniquely well-suited to one or more of these applications, this is not intended to be limiting with respect to all aspects of the inventions described herein.
Mammography is presently the primary method for screening for breast cancer. The primary role of mammography is to screen asymptomatic women in order to detect breast cancer at an earlier stage than would occur with only self-examination and/or clinical breast examination. Detection at an earlier stage of the disease has been shown to reduce or delay mortality from breast cancer.
Mammography uses X-rays to create an image of the interior of the breast. Mammography typically requires careful positioning of the patient by a highly skilled technician trained in mammographic technique. Optimum results depend on pulling and squeezing of the breast during the mammogram, which can be painful. Accurate results are also highly dependent on interpretation of films by a radiologist.
When a patient is screened by mammography, a “suspicious mass” or lesion that is non-palpable (cannot be felt by touch) and not visible to the naked eye is often identified. In these cases, it must be determined whether the lesion is cancerous. This often requires that the lesion or a piece of the lesion be removed for further investigation. To do this, of course, there must be some way that a surgeon can find the lesion in the breast (referred to as “tumor localization” and also as “lesion localization”).
A biopsy is a procedure for removing a portion of the lesion for the purpose of determining whether the lesion is malignant. There are at least three methods of biopsy: open surgical biopsy, core needle biopsy and fine needle (aspiration) biopsy.
For open surgical biopsy, lesion location can be established through a procedure called pre-operative needle localization. Needle localization begins when a specially trained technician puts the breast into a specialized mammography fixture. Several views of the breast are taken using standard mammography to determine the approximate location of the “suspicious mass.”
To locate a lesion, frequently, the breast is squeezed between plates horizontally and one image is taken. The plates are removed and repositioned so that the breast is squeezed vertically and another image is taken and the plates removed again. In addition, multiple images may be taken until the lesion is located. A trained specialist then uses the two (or more) two-dimensional images to estimate where the lesion may be located in three-dimensional space.
A needle is then placed into the breast at the estimated lesion location. The placement of the needle is verified through mammography, again using two or more two-dimensional images. Needle insertion and verification may be repeated until the placement is deemed appropriate by a radiologist. A small wire with a J hook is then placed through the core of the needle. Alternatively, the wire may be pre-loaded in the needle. The needle may be removed and the wire remains. Otherwise, the wire remains in the needle. At this point, the needle localization procedure is complete. The patient is then moved to a surgical setting. During surgery, the wire is used as a guide for the surgeon to cut to the “suspicious mass.” When the surgeon reaches the area where the wire terminates, a tissue sample is taken. The sample is verified to be that of the identified “suspicious mass” by comparing a mammogram of the tissue sample with that of the original mammography.
In practice, depending on breast size, however, there is often as much as a ½ inch movement of the wire before or during the procedure. Accordingly, the sample tissue may not have come from the “suspicious mass.” In those cases, the surgeon may search around the wire termination point and repeat the sample and verification procedure until a match is found. The wire can drift away from its original position in response to motion of the breast. The extent of wire drift may increase as the length of time between localization and surgery increases and as the breast moves. Mammography is used repeatedly in many aspects of breast cancer screening and diagnosis. For example, a dozen mammographic X-rays may be required in support of a single open surgical biopsy.
In core biopsy procedures, a tool is positioned within the breast. The breast is then imaged to determine location of the tool with respect to the lesion. The tool may then be repositioned to more closely target the lesion. This process can be cumbersome and require multiple images of the breast.
In many cases, where the lesion is determined to be cancerous, the lesion must be surgically removed. When the breast is to be largely preserved and only the lesion removed, the procedure is called a lumpectomy. A lumpectomy sometimes requires needle localization as described above. Instead of taking a piece of the “suspicious mass” for analysis, however, the entire mass is surgically removed.
Because the wire may move during or before the procedure due to compression and/or re-compression of the tissue, the biopsy and excision procedures often target the suspicious mass inaccurately. As a result, the procedures may be lengthier than would otherwise be required, occasionally unsuccessful due to failure to accurately localize the lesion, and may result in the unnecessary removal of healthy tissue from the breast. Some (but not all) embodiments of the present invention address one or more of these issues as well as having other advantages that would be apparent to one of ordinary skill in the art based on the disclosure provided herein.